1. Field of the Invention
This invention relates to an electrophotographic recording apparatus which prints characters and graphics on a sheet of paper using electrophotographic technology, and more particularly to a technique of handling the recording paper from the paper stocking position to the printed paper collecting position.
2. Description of the Related Art
In attempts to respond to the needs for high-quality and high-speed printing, electrophotographic recording apparatuses based on the principle of the so-called "xerography" have been developed for practical applications. "Xerography" involves the process in which the optical beam controlled by printing data is irradiated onto a cylindrical photosensitive body to form a latent image thereon; colored toner is caused to adhere electrostatically to the latent image thus formed; and the toner image is then transferred to recording paper to thereby subject the image to a thermocompression bonding.
The printing technique using these electrophotographic recording apparatuses can produce high-density images at high printing speeds per unit time, thereby replacing conventional printing techniques such as offset printing and typography with the so-called desktop publishing in the field of small-scale printing.
In order to provide the best service in such a field of printing, electrophotographic recording apparatuses must be equipped with functions of: printing on both sides of a sheet, sorting the printed sheets by page, printing large amounts of sheets with one supply of sheets, and requiring only a small floor area of installation.
In order to meet these requirements, Japanese Patent Application (UPA) Nos. 167853/1989, 170953/1989 (the term "UPA" as used herein means "Unexamined Published Application") disclose electrophotographic recording apparatuses whose printing path is arranged vertically which causes a printed sheet to be inverted.
These electrophotographic recording apparatuses, allow for the required area of installation to be reduced in proportion to the realized reduction in sheet forwarding floor area.
However, such electrophotographic recording apparatuses have not addressed the problem of sorting the printed sheets by page. The printed sheets are only piled up in the same tray when a large quantity of copies are made.
In addition, these electrophotographic recording apparatuses are available only for cut sheet printing and may not be capable of producing high-quality printing for continuous forms and slips in which positioned entries are required because they may print out of the specified position.
The arrangement of a vertical stacker or stackers in order to reduce the floor area of installation not only causes sheets to be bent due to sheets falling from the sharply standing stacker, but also entails the cumbersome operation of attaching and detaching the stacker to the apparatus body.
In order to overcome these problems, Japanese Patent Application (UPA) Nos. 76073/1989 and 49059/1989 disclose a type of electrophotographic recording apparatus with its stacker(s) arranged horizontally.
However, in such an electrophotographic recording apparatus, the end portion of the cassette containing the recording sheets is located further behind the recording mechanism, and as a result the cassette extrudes from the apparatus body, thereby requiring a larger floor area of installation.